New Contenders For a Theory Of Everything

By GEORGE JOHNSON

Published: December 4, 2001

In science's great chain of being, the particle physicists place themselves with the angels, looking down from the heavenly spheres on the chemists, biologists, geologists, meteorologists -- those who are applying, not discovering, nature's most fundamental laws. Everything, after all, is made from subatomic particles. Once you have a concise theory explaining how they work, the rest should just be filigree.

Even the kindred discipline of solid-state physics, which is concerned with the mass behavior of particles -- what metals, crystals, semiconductors, whole lumps of matter do -- is often considered a lesser pursuit. ''Squalid state physics,'' Murray Gell-Mann, discoverer of the quark, dubbed it. Others dismiss it as ''dirt physics.''

Recently there have been rumblings from the muck. In a clash of scientific cultures, some prominent squalid-staters have been challenging the particle purists as arbiters of ultimate truth.

''The stakes here are very high,'' said Dr. Robert B. Laughlin, a Stanford University theorist who shared a Nobel Prize in 1998 for discoveries in solid-state physics. ''At issue is a deep epistemological matter having to do with what physics is.''

Last year Dr. Laughlin and Dr. David Pines, a theorist at the University of Illinois and Los Alamos National Laboratory, published a manifesto declaring that the ''science of the past,'' which seeks to distill the richness of reality into a few simple equations governing subatomic particles, was coming to an impasse.

Many complex systems -- the very ones the solid-staters study -- appear to be irreducible. Made of many interlocking parts, they display a kind of synergy, obeying ''higher organizing principles'' that cannot be further simplified no matter how hard you try.

Carrying the idea even further, some solid-state physicists are trying to show that the laws of relativity, long considered part of the very bedrock of the physical world, are not platonic truths that have existed since time began.

They may have emerged from the roiling of the vacuum of space, much as supply-and-demand and other ''laws'' of economics emerge from the bustle of the marketplace. If so, then solid-state physics, which specializes in how emergent phenomena occur, may be the most fundamental science of them all.

''We're in the midst of a paradigm change,'' Dr. Pines said. ''Ours is not the prevailing view, but I think it will turn out to be the one that lasts.''

Working in this vein, one of Dr. Laughlin's Stanford colleagues, Dr. Shoucheng Zhang, recently was co-author of a paper suggesting that elementary particles like photons and gravitons, the carriers of electromagnetism and gravity, might not be so elementary after all -- they might emerge as ripples in the vacuum of space, bubbling up from the quagmire in a way that can best be explained in terms of solid-state physics.

''The idea is of course crazy, thought provoking, and somewhat anti-establishment,'' Dr. Zhang said. ''The main idea is to apply concepts from solid-state physics to answer some big questions of the universe.''

The particle physicists insist that there is plenty of mileage left in their own approach. ''I strongly believe that the fundamental laws of nature are not emergent phenomena,'' said Dr. David Gross, director of the Institute for Theoretical Physics at the University of California at Santa Barbara. ''Bob Laughlin and I have violent arguments about this.''

After hearing Dr. Zhang describe his theory at a seminar last month, Dr. Gross deemed it ''an interesting piece of work.'' He said he found the mathematics ''beautiful and intriguing, and perhaps of use somewhere.''

That may sound like faint praise, but the particle physicists have reason to be wary. The squalid-staters are challenging them in a debate over how the universe is made and how science should be done.

Following the method of Plato, the particle physicists are inclined to see nature as crystallized mathematics. In the beginning was a single superforce, the embodiment of an elegant set of equations they call, only a bit facetiously, the theory of everything. Then along came the Big Bang to ruin it all.

The universe cooled and expanded, the single force splintering into the four very different forces observed today: electromagnetism and the weak and strong nuclear forces, which work inside atoms, are described by quantum mechanics and special relativity. The fourth force, gravity, is described by an entirely different theory, general relativity.

The particle physicists' ultimate goal is ''grand unification'' -- recovering the primordial symmetry in the form of a single law -- a few concise equations, it is often said, that could be silk-screened onto a T-shirt.

This approach, in which the most complex phenomena are boiled down to a unique underlying theory, is called reductionism.

The problem, the solid-staters say, is that many forms of matter -- ranging from the exotic like superconductors and superfluids to the mundane like crystals and metals -- cannot be described in terms of fundamental particle interactions. When systems become very complex, completely new and independent laws emerge. ''More is different,'' as the Nobel laureate Philip W. Anderson put it in a landmark paper in 1972. To the solid-staters, it would take something the size of a circus tent to hold all the equations capturing the unruliness of the physical world.

Like Aristotle, they lean toward the notion that it is the equations that flow from nature instead of the other way around. Mathematics is just a tool for making sense of it all.